This program consists of a number of related projects. The basic one is the animal model research with apes at Yerkes. The methods and equipment devised here will be used in research with severely and profoundly mentally retarded subjects at the Georgia Retardation Center and related institutions. The animal model project will concentrate upon a number of topics, including tool use, cognition, numeric learning, acquisition of tenses, pragmatics, spontaneous gestures, and the observational learning skills of an infant chimpanzee being reared with Lana. We will also attempt to define the rudiments of syntax in the operant stimulus-stringing behaviors of small monkeys at Georgia State University. Studies with mental retardates will concentrate upon the continued testing and application of procedures developed in the Yerkes Project. Specific emphasis will be placed upon symbolic problem solving, tool use, receptive capacity, and retrieval skills. This work is designed to elucidate the relationship between cognitive comprehension and the symbolic encoding and use of words. Simple syntactic structures and the refinement of techniques which encourage word combinations also will be studied. An investigation of the social factors which influence language learning (and which are themselves influenced by linguistic skills) will be undertaken with retardates whose pose behavioral management problems. A computerized instruction program (as opposed to the computerized data collection system we now use) will be devised. Initially, this project will provide for computer administered practice of previously learned tasks, but will be developed to foster dialogue-based training programs in which the statements and questions of the computer are dependent upon those of the subject. Through the use of small, lightweight portable conversation boards, we hope to determine whether a keyboard based language-learning approach might be used to enrich familial communication, activities, and commerce of retarded children living at home and attending school during the day.